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Actin is one of the most abundant proteins in eukaryotes and it polymerises to form filament called F-actin. Together with a wide variety of actin binding proteins, F-actin assembles into various complex machineries which generate mechanical tension to accomplish physical tasks including muscle contraction, cell migration and cell division.

Most of eukaryotes so far have been identified have actin orthologues. In mammals, there are 6 isoforms of actin; 4 of them are muscle actin and remaining 2 are ubiquitously expressed non-muscle actin, whereas yeast has one, plant Arabidopsis thaliana has 8 actin isoforms. Due to a divergence of amino acid sequence and patterns of post-translational modification (PTM), actin orthologues and isoforms are varied in biochemical properties and have different affinity to actin binding proteins. This enables organisms to build specialised actin cytoskeletal machineries.

Such beautiful, divergent actin cytoskeletal machineries in wide variety of organisms have attracted many biologists and physicists, and have been studied intensively. However, most of studies used actin purified from rabbit or chicken skeletal muscle instead of original actin orthologues or isoforms due to the fact that preparation of these actin orthologues are difficult. Therefore, we decided to establish a system to express and purify recombinant actin. We have developed new method, PICK-YOUR-ACTIN system using yeast Pichia pastors. This method enables us to express actin in wide-variety of species with appropriate PTMs, and accelerate actin cytoskeleton studies in diverged organisms.